Effect of Three Irrigation Frequencies - Polish Journal of Environmental Studies
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Pol. J. Environ. Stud. Vol. 28, No. 4 (2019), 2363-2370
DOI: 10.15244/pjoes/86124 ONLINE PUBLICATION DATE: 2019-01-23
Original Research
Effect of Three Irrigation Frequencies
on Physiological-Biological Aspects of Young Olive
Trees (Olea europaea L. cvs ‘Koroneiki’
and ‘Picholine’): Vegetative Growth, Leaf Turgor
Pressure, and Fluorescence
Abderrahman Sghaier1, 2*, Hechmi Chehab3, Feten Aissaoui3, 4, Kamel Naggaz2,
Mohamed Ouessar2, Dalenda Boujnah3
1
Faculty of Sciences of Gabes, University of Gabes, Gabes, Tunisia
2
Institut des Régions Arides (IRA), Médenine, Tunisia
3
Laboratoire d’Amélioration de la Productivité de l’Olivier et de la Qualité des Produits,
Institut de l’olivier, Unité Spécialisée de Sousse, Sousse, Tunisia
4
Institut Supérieur Agronomique de Chott Mariem, Sousse, Tunisia
Received: 17 January 2018
Accepted: 1 March 2018
Abstract
In arid and semi-arid areas, farmers are experiencing unprecedented water scarcity, which is likely
to increase by the perspective of global warming. The purpose of this study was to evaluate the effect
of three irrigation frequencies on vegetative growth, leaf turgor pressure, and photosynthesis of young
olive trees (Olea europaea L. cvs ‘Koroneiki’ and ‘Picholine’). We found that throughout the experiment
and for all irrigation treatments, Picholine cultivar showed a higher rate of vegetative growth.
In addition, the leaf turgor pressure for this cultivar showed fewer signs of stress overall as it recorded
less Pp curve inversions during summer. However, during this season the photochemical efficiency
in Picholine for the frequencies T1 and T2 were lower than Koroneiki by 9.53% and 10.63%,
respectively. Which implied that the non-stomatal limitation of photosynthesis has an impact on
Picholine photosynthetic production, which in turn indicates that this cultivar is more sensitive
to high temperature. Moreover, irrigation frequency has little effect on the Koroneiki cultivar.
Keywords: olive trees, irrigation management, water stress, chlorophyll fluorescence
*e-mail: abderrahman.sghaier@gmail.com2364 Sghaier A., et al.
Introduction greenhouse at the specialized unite the Olive Tree
Institute of Sousse in Tunisia (35°49’34”N; 10°38’24”E)
Climate change poses a significant challenge for the from March to November 2015. During the experiment,
entire global world. It’s mainly translated by an increase the plants continued to grow without particular
in temperature and a decrease in rainfall [1]. Thus it has problems.
different effects on environmental degradation, water The experiment was laid out following a split-plot
efficiency, and agricultural productivity [2-4]. Potential design; the main plot units had a 3*2 factorial design
effects of predicted changes are more dramatic for with three irrigation frequencies and two olive cultivars.
arid and semi-arid regions. Reduced water availability Irrigation frequency was the main factor. The split-plot
is among major environmental factors that can greatly units within each main plot consisted of five olive trees.
affect plant production [5]. The most vulnerable plants, Irrigation was designed to deliver 100% of
under extreme drought conditions, are those slow to the available water content (AWC). The irrigation
adapt – like perennial fruit trees [6]. One of the most treatments consisted of irrigating every other day (T0),
important perennial crops at risk in the Mediterranean and irrigating every 4 days (T1) and every 8 days (T2).
region is the olive tree [7] (Olea Europea L.), which is
native to the Mediterranean basin that has considerable Measurement Methods
socio-economic importance. Olive is cultivated in
rainfall conditions due to its minimal requirements Soil Moisture
in water [8]. Olive is well adapted to overcome water
shortages. However, the ability of the olive tree to adapt The volumetric water content of the soil (θv) was
to different drought conditions involves a metabolic cost measured using an SM150T soil moisture (Delta-T
characterized by the diversion of reserves from growth Devices Ltd., Cambridge,UK) probe every other day
and a reduction in leaf area, which cause a significant throughout the experiment period for all pots. It was
reduction in productivity [9]. On the other hand, the measured with a soil moisture sensor.
severity of future drought projections due to fast global
environmental change puts the olive in serious danger Plant Growth and Environmental Measurements
[10]. So it is necessary to adapt olive crops to a situation
of sustainability that obtains a certain trade-off between Apical growth was measured every 2 weeks from
productivity and water availability. the 15th of May to the 15th of November 2015. The
In recent decades, several studies have been measurements were performed on all the trees.
carried out to propose solutions to grow olives under Air temperature and relative humidity in the
water scarcity so that we can adapt olive crops to a greenhouse were measured instantaneously throughout
situation of sustainability that obtains a certain trade- the period of the experiment using sensors installed
off between productivity and water availability. Most in the middle of the greenhouse. The data was saved
of those studies focused either on comparing different by a data logger equipped with a wireless transmitter
deficit irrigation levels on olive tree [11-13], comparing connected to a control unit in the laboratory.
how different genotypes cope with water stress [14-
16], or on the physiological response to sustained water Leaf Turgor Pressure
deficit and subsequent re-watering [17, 18], despite many
studies having shown that irrigation frequency affects Two trees per treatment were equipped with an
photosynthesis, leaf gas exchange, vegetative growth, LPCP probe (probes provided by ZIM Plant Technology
and yield of other species under water stress [19]. The GmbH, Hennigsdorf, Germany). The probes were
effect of irrigation frequency has not yet been studied on clamped on leaves on the Northeast side of the tree.
vegetative growth and olive tree yield. The aim of this Installation was done as recommended by Zimmermann
study was to evaluate the effect that irrigation frequency [20]. The output pressure probes were adjusted to be
has on vegetative growth, leaf turgor pressure, and between 10 and 25 kPa by adopting an appropriate
fluorescence of olive tree (Olea europaea L.) cultivars distance between the two magnets. The probes were
Koroneiki and Picholine. clamped between the central nerve and the leaf margins
to establish a uniform contact with the leaf tissue.
The magnets containing the pressure sensor were placed
Material and Methods on the abaxial leaf surface. Probes pressure recordings
were sent every 5 minutes via a wireless transmitter to
Experimental Setup a base station, which is connected to an Internet server
of the company ZIM Plant Technology GmbH. This
One-and-a-half-year-old rooted cuttings of the olive allows monitoring and control of experimentation
(Oleaeuropaea L.) cultivars Koroneiki and Picholine through any computer connected to the Internet.
were grown in 20-L plastic pots containing freely Certain probes were accidentally detached because of
drained light soil, with a pH of 7.6, a field capacity the usual work in the greenhouse. Also, wind and dust
of 35%, and permanent wilting point of 15% in a accumulation caused poor contact between the probesEffect of Three Irrigation Frequencies... 2365
and leaves. This malfunction of the probes led to the
loss of data from these probes for short periods. In these
cases, the probes were removed, cleaned, and attached
to the leaves well.
Fernandez [21] revealed a correspondence between
the midday stem water potential (ψswp) and changes
of the Pp value over a period of several days. He
found three states of stress corresponding to three
specific ranges of ψswp. Furthermore, Ehrenberger [22]
characterized these states with more details:
–– State 1: low water stress, the leaf is in a turgescent
state characterized by a reciprocal dependency of Pp
on turgor pressure (Pc values larger than 50 kPa).
This state corresponded to a ψsw under −1.2 MPa.
–– State 2: moderate water stress, the turgor pressure
in the leaf is low. This state is characterized by
an unfavorable ratio of air to water in the leaf. It
represents an intermediate state between States 1 and
3, and the Pp curve is semi-inversed. It corresponded
to a ψsw ranging from −1.2 to −1.7 MPa.
–– State 3: severe water stress, the leaf is significantly Fig. 1. Average apical growth of the two olive cultivars
dehydrated (air is accumulated in the leaf tissue) and (Koroneiki and Picholine) at irrigation frequencies T0, T1, and
the turgor pressure values close to zero: this state is T2 (means with the same letter are not significantly different at
P≤0.05)
denoted by the inversion of the Pc curves (Pp records
minimum values at noon and maximum values
during the night). This state corresponded to a ψsw
below −1.7 MPa. significant for nearly all dates and times in the day, so
their effect can be assumed to be independent enough to
Photochemical Efficiency of PSII allow the study of each factor separately.
For frequencies T1 and T2, the Koroneiki cultivar
The fluorescence parameters (F0: initial fluorescence showed a close vegetative growth rate (Fig. 1).
and Fm: maximal fluorescence) were measured with These results were supported by the results of leaf
a mobile chlorophyll fluorometer (OS1-FL Opti- turgor pressure (Koroneiki cultivar showed state 3 under
Sciences) on two leaves by olive-tree and two olive- both T1 and T2 treatments; Fig. 2).
trees by irrigation treatment [23]. These parameters Picholine, on the other hand, showed a significant
were taken at noon at a suitable angle for ambient light difference depending on the irrigation schedule. Thus
to penetrate up to the leaf surface. The probe is kept for this cultivar, the growth rate was in clear correlation
stable during measurements to avoid disturbance [24]. with the water treatment. These results fit with the
The photochemical efficiency of photosystem II (PS II) results of the leaf turgor pressure for this cultivar where
was estimated from a ratio of variable fluorescence to state 3 appeared only in trees under T3 treatment. The
maximum fluorescence (Fv / Fm = (Fm-F0) / Fm) [25]. vegetative growth in Picholine cultivar is consistent with
that found by Aïachi-Mezghani [26]. Irrespective of the
Statistical Analysis time lag between irrigation, Picholine cultivar showed
growth rates higher than the Koroneiki cultivar. Those
A two-way analysis of variance (ANOVA) was used higher rates can be explained by the genetic background
to examine the effect of cultivars and doses of irrigation of each cultivar [27]. Moreover, Picholine appears to have
on all parameters studied. The differences between higher rates even when subjected to water stress [16, 28,
irrigation treatments were compared using Tukey’s test 29]. The different growth dynamic may be due to the
calculated at p2366 Sghaier A., et al.
Fig. 2. Daily curves of the output probe’s pressure (Pp) in Koroneiki (a, c, and e) and Picholine (b, d, and f) cultivars for frequency of
irrigations T0 , T1, and T2; the tree state per irrigation treatment and cultivar are shown here by horizontal color bars through State 1 (low
water stress: green), State 2 (moderate stress: yellow), and State 3 (severe stress: red).
by the result of the soil moisture, where means of soil three seasons of the experimentation for Picholine and
moisture are higher in pots of Koroneiki cultivar than Koroneiki.
in pots of Picholine for all irrigation frequencies (Fig. During the springtime, a high positive correlation
3). The lack of correlation between the growth rate and was recorded between the pressure peaks of leaf
the water treatment among the Koroneiki cultivar can be turgidity (TFP) and water treatment in both cultivars.
explained by the effect of annual alternation, which can The peaks of diurnal pressure, the minimum values
be accentuated under water deficit conditions [31]. of nocturnal pressure, and amplitudes of leaf turgor
As discussed by Fernández [32], the ZIM system pressure are indicators of moderate water stress [35].
is a practical technique for monitoring water stress. In For T1 these indicators were very close to the control
addition, it is capable of detecting the stress in early treatment (T0) in both cultivars. They are similar to that
stages when it was still possible to prevent their effects recorded by Ehrenberge [22] in non-stressed trees. In
on growth [17, 33, 34]. addition, the irrigation event in the fourth day induces a
The result of the leaf turgor pressure shows slight decrease in both diurnal and nocturnal extremities
significant changes in both absolute values and Pp for both cultivars. This result suggests that treatment T1
curves depending on the season. Fig. 2 represents a Part does not induce stress in suitable climatic conditions.
of the long-term Pp measurements recorded during the For the irrigation schedule T2, the daily means of turgorEffect of Three Irrigation Frequencies... 2367
the Pp curve. As the semi-inversion, the full-inversion
is reversible too [40]. Nevertheless, if the plant did not
rehydrate soon, permanent damage can occur. This
phenomenon was more frequent in Koroneiki cultivar.
The reason behind this behavior could be the tendency
of the Koroneiki cultivar to have less dense mesophyll
cells compared to other cultivars when subjected to
water stress [16]. Hence, there are more air spaces in the
spongy mesophyll tissue in Koroneiki’s leaves, which
is the main reason for the inverse diurnal Pp curves
[40]. Nevertheless, if the plant did not rehydrate soon,
permanent damage can occur. This phenomenon was
more frequent in Koroneiki cultivar. The reason behind
this behavior could be the tendency of the Koroneiki
cultivar to have less dense mesophyll cells compared
to other cultivars when subjected to water stress
[16]. Hence, there are more air spaces in the spongy
mesophyll tissue in Koroneiki leaves, which is the main
reason for the inverse diurnal Pp curves [40].
During autumn, Pp curves showed a pattern similar
to that recorded during the spring. Thus, state one was
dominant within a few days of state two. However,
Fig. 3. Changes in soil water content (%) in Koroneiki a) and the Pp recorded values higher than expected. This can
Picholine b). be explained by the changes in the structure and the
mechanical characteristics of the olive leaf throughout
the experiment. Thus, as the experiment was conducted
during a relatively long and stressful period, the absolute
pressure was higher for both cultivars. In the sixth and
Pp values may be affected by the damaged palisade
seventh days after irrigation, daytime peak pressures
parenchyma due to water stress [34].
increased to reach values over 80 kPa and basic turgor
Picholine cultivar shows averages of the
recorded values close to 50 kPa, indicating moderate
photochemical efficiency of PSII (Fv/Fm) between
stress state [21, 36]. In addition, the rate of the decrease
0.658 and 0.851, while averages of the photochemical
in patch pressure afternoon peaking rises along with
efficiency of PSII (Fv/Fm) for the Koroneiki cultivar
the decrease in water content. According to Bramley
appear between 0.696 and 0.843 (Fig. 4). During spring
[37], this indicates slight water stress. Therefore, state
and autumn, the photochemical efficiency was higher in
one was observed in the majorities of the days and state
Picholine cultivar than in Koroneiki. On the other hand,
two was observed a few days before re-watering. In
during summer the fluorescence activity was more
both irrigation frequencies T1 and T2, the trees recover
affected in Picholine cultivar. These results fit with the
quickly after irrigation and return to state one.
result of vegetative growth, leaf turgor pressure, and soil
During the summer, when the temperature can
water content. This photochemical efficiency behavior
reach 50°C, Koroneiki and Picholine exhibited different
supports the suggestion given above that the inhibition of
reactions. Picholine cultivar under T1 treatment showed
photochemical reactions has a greater impact on limiting
that extreme temperature only induces an increase in
the development of this cultivar. The photochemical
both daytime peak pressures and basic turgor following
efficiency for the Koroneiki cultivar appeared to be less
the irrigation schedule. However, Koroneiki under
sensitive to the season rather than the water treatment.
the same water treatment showed that as it becomes
These results show clear accordance with the results
more difficult for leaves to rehydrate with increasing
discussed above. From the results obtained in both
soil water deficit, Pp values recorded a peak value
cultivars, during the summer there was a dramatic
during the afternoon, followed by an increase during
decrease in the photochemical efficiency of PSII
the night – a phenomenon known as semi-inversion of
(Fv/Fm) proportional to water availability (Fig. 4). The
the Pp curve [38]. Even though this is reversible when
same phenomenon was observed in the work in other
the plant rehydrates depending on the schedule, it can
olive cultivars [41]. Any time this reduction was greater
affect the productivity of the plan [39]. Unsurprisingly,
in the Picholine cultivar. According to Angelopoulos
under treatment T2 where the rehydration of trees was
[18] and Sofo [42], such as the reduction of the ratio (Fv/
less frequent, both cultivars recorded minimum values
Fm), shows that the plant is under a severe water stress,
during daytime, which can be explained by large air
which can induce a certain level of photo-inhibition.
spaces in the leaf and a maximum value during night-
The tree can recover partially four to five days after re-
time due to the reduction of the air spaces volume by
irrigation.
some water. This behavior indicates a full inversion of2368 Sghaier A., et al.
Conflict of Interest
The authors declare no conflict of interest.
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